A struct is a composite type that groups related fields together — Go's way to define custom data types and model entities. Since Go has no classes, structs (plus methods) are how you do object-oriented-style programming.
Person {
Name
Age
email
}
p1 := Person{Name: , Age: }
p2 := Person{, , }
p3 Person
p1.Name
p1.Age =
Capitalized field/type/func name → EXPORTED (public, usable outside the package)
lowercase name → unexported (private to the package)
Go uses capitalization, not keywords, for visibility — a distinctive convention.
// a method is a function with a RECEIVER (the struct it operates on)
func (p Person) Greet() string { // value receiver
return "Hi, I'm " + p.Name
}
func (p *Person) Birthday() { // pointer receiver — can MODIFY the struct
p.Age++
}
p1.Greet() // "Hi, I'm Ann"
p1.Birthday() // modifies p1 (Go auto-takes the address)
Methods attach behavior to structs via a receiver. Pointer receivers (*Person) let methods modify the struct; value receivers get a copy.
p1 := Person{Name: "Ann"}
p2 := p1 // COPIES the entire struct (independent)
p2.Name = "Bob"
fmt.Println(p1.Name) // "Ann" — unchanged (it was a copy)
// pass a pointer to share/modify
func update(p *Person) { p.Name = "X" }
Assigning or passing a struct copies it (value semantics) — to share or modify, use a pointer.
type User struct {
Name string `json:"name"` // tags guide encoding/decoding
Email string `json:"email,omitempty"`
}
Tags attach metadata (used by JSON, DB, validation libraries) read via reflection.
Structs are the core way to model data and build custom types in Go — and combined with methods, they're how Go does object-oriented-style programming (it has no classes).
Understanding struct definition, the capitalization-based visibility convention (unique to Go), value semantics (assignment copies — so use pointers to share/modify, a common gotcha), methods with value vs pointer receivers, and struct tags (for JSON/DB mapping) is fundamental to nearly all Go code.
Structs appear everywhere — domain models, configuration, API payloads, data structures — making them essential, everyday knowledge for working effectively in Go.